Modelling magnetization processes in single-and multi-domain rock samples using the preisach diagram

Summary The paper presents the results of identifying a model of the Preisach type for haematite grains of the single-domain as well as multi-domain size. Due to the phenomenological conception of the model, the relations between the parameters of the model and actual parameters are very complex, however, impressive accuracy and stability of the modified model indicate the need to resume studies of this problem. The model parameters also confirm the adequate properties of the vibrating-sample magnetometr (VSM) used and developed in our laboratories.     

Observational Tracking of the 2D Structure of Coronal Mass Ejections Between the Sun and 1 AU

The Solar TErrestrial RElations Observatory (STEREO) provides high cadence and high resolution images of the structure and morphology of coronal mass ejections (CMEs) in the inner heliosphere. CME directions and propagation speeds have often been estimated through the use of time-elongation maps obtained from the STEREO Heliospheric Imager (HI) data. Many of these CMEs have been identified by citizen scientists working within the SolarStormWatch project ( www.solarstormwatch.com ) as they work towards providing robust real-time identification of Earth-directed CMEs. The wide field of view of HI allows scientists to directly observe the two-dimensional (2D) structures, while the relative simplicity of time-elongation analysis means that it can be easily applied to many such events, thereby enabling a much deeper understanding of how CMEs evolve between the Sun and the Earth. For events with certain orientations, both the rear and front edges of the CME can be monitored at varying heliocentric distances (R) between the Sun and 1?AU. Here we take four example events with measurable position angle widths and identified by the citizen scientists. These events were chosen for the clarity of their structure within the HI cameras and their long track lengths in the time-elongation maps. We show a linear dependency with R for the growth of the radial width (W) and the 2D aspect ratio (??) of these CMEs, which are measured out to ???0.7?AU. We estimated the radial width from a linear best fit for the average of the four CMEs. We obtained the relationships W=0.14R+0.04 for the width and ??=2.5R+0.86 for the aspect ratio (W and R in units of?AU).     

The Application of Petroleum Hydrocarbon Fingerprint Characterization in Site Investigation and Remediation

Tremendous resources have been and continue to be spent investigating and remediating petroleum hydrocarbon compounds (PHCs) in soil and ground water. Investigating and planning a remedial strategy for sites affected by PHCs is often a challenging task because of the complex chemical nature of the PHCs. the complex regulatory environment related to PHC cleanup, and the use of analytical methods that provide quantitation but not identification of PHCs. From a technical standpoint, the PHC impacting soil and/or ground water is frequently inadequately characterised, both in identification as well as in is general properties (solubility, toxicity). From a regulatory standpoint, promulgated or recommended total petroleum hydrocarbon (TPH) cleanup levels generally relate to assumed properties of specific unweathered products and are inconsistent among different agencies and regions. This produces a prime situation for unwillingly spending more resources on investigation or remediation than may be necessary, especially when the PHC in the subsurface has different properties from unweathered products such as gasoline or diesel.
Accurately identifying the PHC and its nature, a process known as fingerprint characterization, is critical to the determination of appropriate regulatory goals and design of cost-effective remedial approaches. This paper presents several case studies in which fingerprint characterization made a significant difference in the project outcome. In each instance the nature of the organic material was better understood, the regulatory cleanup levels were negotiated based on the nature of the material, and a remedial approach was implemented that differed significantly from and was generally less costly than what would have been required without fingerprint characterization data.     

Timing and mechanisms controlling evaporite diapirism on Ellef Ringnes Island,Canadian Arctic Archipelago

The Permo‐Carboniferous to Eocene Sverdrup Basin in Canada's Arctic Archipelago is strongly influenced by evaporite diapirism. However, salt structures within the basin have not been extensively investigated recently due to their remote location. This study includes the interpretation of legacy seismic reflection and borehole data to characterize the geometry of selected evaporite domes, and 1D backstripping of wells to investigate tectonic and sedimentary influences on diapirism. Extensional rift‐structures appear to have played a significant role in the formation of evaporite domes by triggering and directing salt movement. Diapirism was initiated by at least the Middle Triassic and continued to develop during the Mesozoic. Differential loading of salt on opposing east–west dome margins led to their present day asymmetric geometries. Diapir growth rates in the Mesozoic were closely linked to the rate of sedimentation and influenced by regional tectonism.     

Simultaneous exposure of English sole (Parophrys vetulus) to sediment-associated xenobiotics: Part 1—uptake and disposition of 14C-polychlorinated biphenyls and 3H-benzo[a]pyrene

English sole (Parophrys vetulus) were exposed to environmentally realistic levels of sediment-associated ³H-benzo[a]pyrene (3 μg BaP/g sediment, dry weight) and ¹⁴C-Aroclor 1254 (1 μg PCBs/g), separately and together, for up to 10 days. BaP and its metabolites in tissues reached steady-state concentrations by the first day of the exposure, whereas PCBs did not approach steady-state concentrations until the tenth day of exposure. Simultaneous exposure of sole to BaP and PCBs, relative to separate exposure to the xenobiotics, significantly increased the concentrations of BaP-derived radioactivity and decreased the concentrations of PCB-derived radioactivity in some tissues and bile. Accumulation of PCB-derived radioactivity, estimated as the burden in tissues, was significantly greater (4- to 13-fold) than that of BaP-derived radioactivity throughout the experiments and regardless of the type of exposure. The rank of the concentrations of PCB-derived radioactivity in tissues and bile was: bile ～ liver > brain > kidney ～ gill > skin ～ blood ～ muscle and for BaP-derived radioactivity the order was: bile > liver > gill > kidney > skin ～ blood > muscle > brain. BaP-derived radioactivity in liver and bile was present primary (85–99%) as metabolites, whereas PCB-derived radioactivity was present equally as parent compounds and metabolites in bile and primarily (98 %) as parent compounds in liver. Hydrolysis of bile from PCB/BaP-exposed sole with β-glucuronidase/arylsulfatase released 35 % of the BaP-derived radioactivity and 32 % of the PCB-derived radioactivity as primary metabolites. A much higher proportion of the BaP-derived radioactivity (64 %) than the PCB-derived radioactivity (13 %) in bile was unaffected by the enzyme treatment, indicating differences in the conjugation of the primary metabolites of PCBs and BaP. The results suggest that in contaminated environments the tissue to sediment concentration ratios for PCBs would exceed that for BaP and its metabolites; however, BaP would be continually absorbed and metabolized by sole to potentially carcinogenic and mutagenic compounds. In addition, the tissue levels of these toxic compounds may be increased by simultaneous exposure to PCBs.     

Spatiotemporal aspects of silica buffering in restored tidal marshes

Losses of pelagic diatom production resulting from silica limitation have not only been blamed for toxic algal blooms, but for the reduction in ability of coastal food webs to support higher trophic levels. Recent research has shown the importance of advective seepage water fluxes of dissolved silica (DSi) from freshwater marshes to pelagic waters during moments of riverine Si-limitation. In this study, we investigated the potential impact of recently installed new tidal areas along the Schelde estuary, located in former polder areas and characterized by so-called controlled reduced tidal regimes (CRT). Nine mass-balance studies were conducted in a newly constructed CRT in the freshwater Schelde estuary. During complete tidal cycles both DSi and amorphous silica (ASi) concentrations were monitored at the entrance culverts and in different habitats in the marsh. A swift DSi-delivery capacity was observed despite the shifted spatiotemporal frame of exchange processes compared to reference marshes. As silica-accumulating vegetation is not yet present, and difference with reference marshes’ deliveries is surprisingly small, we indicate diatomaceous debris and phytoliths to be the main silica source. Although further research is necessary on the driving forces of the different processes involved, restoration of former agricultural areas under CRT-regime provide the potential to buffer silica in the estuary.     

Assessment of boundary-element method for modelling a free-floating sloped wave energy device. Part 1: Numerical modelling

The boundary-element method has been widely used as a design tool in the offshore and ship building industry for more than 30 years. Its application to wave energy conversion is, however, more recent. This paper deals with the numerical modelling of a free-floating sloped wave energy device. The power take-off mechanism of the device consists of an immersed tube with a piston sliding inside. The modelling is done using the boundary-element method package WAMIT. The model is first worked out for the case where the axis of the tube is vertical. It is then derived for the tube inclined and successfully verified against numerical benchmark data. A companion paper presents results of a detailed comparison with a physical model study.